1. Field of the Invention
The present invention relates generally to apparatus for recognizing graphic data, and more particularly to a character recognition apparatus that recognizes characters by comparing data representative of an unknown character and stored data representative of selected characters in a serial manner.
2. Description of the Prior Art
Heretofore, devices have been available for recognizing graphic data such as characters, letters, numerals, marks, symbols, fingerprints, etc. Such devices are used as label readers, as feeders for computing machines, as comparators for checking the similarity between thumb prints, and as card readers to prevent unauthorized access to industrial plants or military installations.
One type of prior art device for recognizing characters uses analog components to compare a train of electrical pulses derived from scanning an unknown character with various trains of pulses derived from information stored on a magnetic drum memory, each of which is representative of a different known or reference character. The comparison between the unknown character and all the known characters occurs in a parallel manner. Those pulses of each known train which are coincident in time with pulses of the unknown train are ignored, and those pulses which are not coincident in time are counted. The number of pulses counted provides an indication of the differences between the unknown character being examined and the reference character with which it is compared. In this manner the unknown symbol is identified by a process of elimination, or rejection of all known characters which differ. However, such a device has been found to be undesirable since it operates on an analog video signal and consequently requires many relatively complex video comparators and amplifiers because of the simultaneous parallel comparisons. Another disadvantage of such a device is that the magnetic drum memory that is required to store the complex video signals is relatively large and consequently expensive.
Examples of such prior art devices are found in U.S. Pat. Nos. 3,713,099 and 3,713,100, each of which is entitled "Method and Apparatus for Identifying Letters, Characters, Symbols and the Like" by Harold S. Hemstreet.